Reductions in Climate Zone Changes Under Stratospheric Aerosol Injection Compared to Unabated Warming

Abstract

As the goals of the Paris Agreement struggle to be met, interest in stratospheric aerosol injection (SAI) has increased due to its potential to reduce the impacts of anthropogenic warming. SAI would aim to cool the Earth by injecting sulfate aerosols or their precursors into the stratosphere, reflecting incoming sunlight back to space. Previous work has shown that SAI could produce regionally varying temperature and precipitation impacts, however, along with global mean drying. Climate classification systems serve as a potentially useful tool in quantifying how concerning these impacts may be. We evaluate the effectiveness of SAI by identifying the types and magnitude of climate zone changes over time, which we term “adaptation burdens.” A modified version of the Köppen-Trewartha climate classification system is used to identify changes in climate zones under a high greenhouse gas emissions scenario, a medium emissions scenario, and a scenario in which SAI is implemented such that global mean temperature follows that of the medium emissions scenario despite high greenhouse gas emissions. We find that changes in climate zones under this SAI scenario are similar in both magnitude and transition type to those under medium-tier emissions, while shifts under high emissions are significantly greater in magnitude and diverge further from the historical baseline. While all models analyzed agree that SAI reduces adaptation burdens in comparison to a high emissions scenario, they disagree on magnitudes and regional distributions, indicating differing model responses to aerosol and greenhouse gas forcings.